Islam et al., 2000. Asian-Aust. J. Anim. Sci., 13 (7): 941-947

Three fistulated Malaysian local bulls were used in a 3 * 3 Latin square design to determine the effects of different levels of concentrate with oil palm (Elaeis guineensis) frond (OPF) on rumen pH and NH 3-N concentration, and DM degradability of different fractions of OPF. Three diets namely, 60% OPF pellet and 40% concentrate (diet 1), 50% OPF pellet and 50% concentrate (diet 2) and 40% OPF pellets and 60% concentrate (diet 3) were used. The levels of concentrate in the diets affected rumen pH and NH 3-N concentration. The pH and NH 3-N concentration in almost all hourly samples did not show any difference among diets except the 6-h and 9-h samples. The highest (p<0.01) NH 3-N concentration was obtained on diet 3 followed by diet 2 and diet 1, but there was a slightly higher (p>0.05) pH on diet 1. The NH 3-N concentrations of rumen liquor at 9 h sampling on diet 1 and diet 2 were below the critical level (50 mg/litre) required for efficient fermentation of fibrous feeds. The  in sacco DM degradation of different fractions of OPF was affected by diets. The DM degradation of fractions of OPF was higher on diet 3, which showed differences (p<0.01) from the other diets. It was found that a higher level of concentrate (60%) with OPF gave a higher rumen NH 3-N concentration that increased the DM degradation of OPF fractions. The results showed that OPF could support an efficient rumen function in terms of NH 3-N concentration and pH when ≤50% in the diet. A higher level of OPF (>50%) does not support an efficient rumen fermentation in terms of NH 3-N concentration, and resulted in lower DM degradation values of the fractions. The results suggested that there is a need to supplement additional nitrogen to OPF based diets.